This invention relates to an arcing chamber for electric power circuit breakers, especially fast acting D.C. breakers, in which a wedge-shaped arcing space is defined by perforated, sieve-like, ceramic plates.
Such an arcing chamber has been described in the German Offenlengungsschrift No. 19 33 529 in which the perforated plates enable pressure equalization to occur, so that the travel of the arc is not impeded. In the process, arc gases pass through the holes in the perforated plates and are cooled and deionized. In spite of these good properties of the ceramic sieve, it has been found that only a limited number of circuit interruptions can be performed, since, under the influence of the heat of the arc, the surfaces of the ceramic sieve plates become vitrified and the holes are partially or totally closed off. Attempts to avoid this vitrification by enlarging the holes have been unsuccessful, since the flow of gas through the holes became so heavy that, due to continued ionization, breakdowns occurred outside the arcing space with consequent failure of the breaker.
It is an object of the invention to maintain a large quenching capacity in the arc chamber while preventing clogging of the holes in the ceramic sieve; at the same time, ejection of gas to the outside of the arcing chamber is reduced to such an extent that little spacing between it and nearby grounded parts is needed.